Hi,
I was out riding today when all of a sudden the bike shut down and started smoking. I've ridden about 500 miles so far this year with no issues. Looks like I really fried the wiring harness, I was able to trailer it home and take pictures. I don't know why this happened or how, but here are some pics of what it looks like now - it's not pretty. Hoping to get some repair advice and maybe discover what caused this. After I got the bike back home I went to check the dog bone fuse, and I can't find it - wondering if PO pulled it and did not replace with anything? Thanks, looking forward to your response.

Hi,
I was out riding today when all of a sudden the bike shut down and started smoking. I've ridden about 500 miles so far this year with no issues. Looks like I really fried the wiring harness, I was able to trailer it home and take pictures. I don't know why this happened or how, but here are some pics of what it looks like now - it's not pretty. Hoping to get some repair advice and maybe discover what caused this. After I got the bike back home I went to check the dog bone fuse, and I can't find it - wondering if PO pulled it and did not replace with anything? Thanks, looking forward to your response.

The relay was installed so the regulator could read the voltage directly from the battery. Actually the wire coming from the harness, connected to the relay, and that relay wire are completely fried. The connector between those wires melted off.

Wouldn't be surprised if it was a catastrophic rectifier failure. If one diode shorts out the bike would still run but the charging would be seriously compromised, and the remaining five diodes and the stator would be stressed. But if another diode shorts on the opposite rail (+ or -) then battery voltage has a direct path to ground thru the shorted diodes, and SHOULD blow the main fuse, or in your case, wiring harness.

Yup, from that last picture, it appears as someone has cut out the main fuse and replaced it with just a piece of wire - so no main fuse. Then you had a dead short to ground somewhere, and this is the result. Sorry to see it!

I've ordered a harness from ebay, it should get here next week. I'm a novice when it comes to electric but I think I can handle it. I've been reading and re-reading WingAdmin's Electric 101 posts as well (thanks for that).

Is there anything I should be doing now, before the new harness gets here?

Any tips on installing the new harness?

Are the diodes in the rectifier?

I found a bit of a rat's nest behind the headlight. Broken ground, some exposed wiring and corrosion on a connector:

I've ordered a harness from ebay, it should get here next week. I'm a novice when it comes to electric but I think I can handle it. I've been reading and re-reading WingAdmin's Electric 101 posts as well (thanks for that).

Is there anything I should be doing now, before the new harness gets here?

Any tips on installing the new harness?

Are the diodes in the rectifier?

I found a bit of a rat's nest behind the headlight. Broken ground, some exposed wiring and corrosion on a connector:

Headlight rat's nest.jpg

Headlight connector corrosion.jpg

Did you get a NEW harness or another 40 year old one?

Inspect it very carefully for any breaks or cuts.

A lot of them have suffered injuries from the dreaded 70s era scotch locks.

Thanks for the advice. I ordered a 40 year old harness because I couldn't find a new one. Are you aware of a source for a new one?

No, that's why I ask.

I do know of people who have made their own.

I'd be sorely tempted to take that 40 year harness apart, blueprint it, then build a jig from it so that I could build a new one, with brand new wire and connectors, and maybe some larger gauge wire while I was at it.

Thanks for the advice. I ordered a 40 year old harness because I couldn't find a new one. Are you aware of a source for a new one?

No, that's why I ask.

I do know of people who have made their own.

I'd be sorely tempted to take that 40 year harness apart, blueprint it, then build a jig from it so that I could build a new one, with brand new wire and connectors, and maybe some larger gauge wire while I was at it.

Just to follow up, I pulled the old wrapping off the new (used) harness, checked all connections, checked continuity, re-wrapped and installed it and it worked! I had to replace a couple of plug connectors, and a few bad wires in the sub harnesses that needed repair. I spent a lot of time reading the color schematic and ended up with a pretty good understanding of where the wires go and what they do. I also went with regulator/rectifier unit and eliminated the voltage regulator. So far seems to be charging as it should.

For someone who knew next to nothing about the electrical system I think the repair went well. It really wasn't that difficult once I began to understand the schematic. Thanks again for the advice.